The present invention relates to welding equipment, and more specifically ceramic wire feeding rollers which possess a longer wear life than metallic wire feed rollers and which prohibit welding wire from slipping in a roller assembly.
A long recognized need in the wire feed roller industry, specifically with robotic MIG welders, is for wire feed rollers that do not wear out and allow the welding wire to slip in the roller assembly. To date, wire feed rollers are fabricated from various metallic materials which are life limited due to active wear mechanisms within the metallic materials. As the wire is fed through the rollers, high tangential shear stresses between the welding wire and the rollers results in material removal from the rollers. When a sufficient amount of material is removed, the clamping, or contact, load is reduced due to the increased clearances and the wire begins to slip in the rollers. Further, as the rollers wear, the contact surface becomes smooth effectively reducing the friction coefficient between the wire and the roller contact surface. If an increase in the clamping load is not made via tensioning adjustments, as found on many assemblies, the wire will fail to feed to the weld tip, thus causing an interrupted weld and entanglement, or balling, of the wire in the wire feed mechanism. This action results in costly equipment downtime and repair to interrupted weldments.
To enhance the functional life of metallic rollers, surface features are sometimes added to the contact surfaces to aid in gripping the wire. These surfaces too, are subject to wear through continuous welder usage which effectively eliminates any functional advantage. Since all metallic materials have active wear mechanisms (i.e., slip plane movement, dislocation movement, grain boundary movement, low relative compressive strength, low relative surface hardness, etc.), a specific high friction surface finish/feature cannot be maintained for extended usage periods.
It can be seen therefore that a need exists for wire feed rollers that possess significantly longer wear life than existing metallic rollers both to eliminate equipment downtime and to maintain continuous weld integrity. Further, reduced drive load requirements for wire feed roller drive motor assemblies and a sustainable clamping load regime that would not require regular tensioning adjustments to ensure welding wire slippage is minimized would be useful to the wire feed and welding equipment industries.